As a means of decorations or of showing the name of, and/or instructions on, a product on one side or both sides of a body of a synthetic resin blow-molded product, much use is made of those means of adhering the labels on which decorative patterns, product name, instructions, and the like, are printed. As a method of attaching labels there is an in-mold labeling process, which comprises using what is called the in-mold labels (hereinafter at times referred to simply as the labels) as an insert material, setting previously the labels inside a mold, and adhering the labels to outer peripheral wall surfaces of a container main-body just when the main body is molded.
This in-mold labeling process has the following distinguished features: 1) Labels are adhered to the container main-body concurrently when the main body is being molded, thus requiring no adhering work in another exclusive process step; 2) since there is no different level in height between the container main-body and the labels, there is no risk of damaged external appearance and/or a sense of discomfort to the touch; and 3) strong and steady adhesion to the main body is available, regardless of thin wall found in today's blow molded containers. Patent document D1, for example, describes an invention on in-mold labels, a labeled and blow molded product, and a process for manufacturing such a product.
FIGS. 13(a), 13(b) and 13(c) are vertical sections showing three examples of basic laminar structures for in-mold labels that have been in general use conventionally. The label 111 of FIG. 13(a) comprises a clear substrate layer 112 made of an unstretched cast polypropylene film (hereinafter referred to as the CPP film), a gravure printed layer 113 formed on the back of the substrate layer 112, and an adhesive layer 116 made of a polyethylene series resin laminated by an extrusion laminate processing method. The label 111 of FIG. 13(b) comprises a clear substrate layer 112 of a CPP film, a gravure printed layer 113 formed on the back of the substrate layer 112, and an adhesive layer 116 made of a copolymerized PP resin film laminated through an intermediary of a dry laminate layer 115.
The label 111 of FIG. 13(c) comprises a substrate layer 112a of a synthetic paper, a heat-sealed adhesive layer 116 laminated on the back of the substrate layer 112, a flexography printed layer 113 formed on the surface of the substrate layer 112, and a clear protective layer 117 that covers the printed layer 113.